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Sure-Grip Power Chucks from Hardinge Inc. is a premiere line of lever-operated, counter-centrifugal and dynamically balanced chucks. The lever-operated design has several advantages over the wedge-type design most commonly found on low cost, non-counterbalanced chucks that are supplied with the initial purchase of many chuck-style lathes.

In the lever-operated system, the drawtube is connected to the jaws through a pivoting lever that is mounted on pins inside the chuck body. The lever system has reduced friction and increased mechanical advantage compared with a wedge-operated chuck for a given drawbar pressure, Hardinge says.

The lever system also has reduced internal bearing surface over the wedge-operated closure, making it less sensitive to lack of lubrication. The better efficiency of the design results in reduced wear on the operating cylinder, dramatically increasing component life. For this reason, a lever-operated chuck system (chuck and operating cylinder) will usually have a longer life than that of a wedge-operated system.

In the Hardinge counterbalanced chuck design, weights are incorporated into the actuating levers of the chucks at the opposite end of the fulcrum or pivot-point of the jaws. Centrifugal force acts upon this weight just as it does on the top jaws. However, since the weight is at the opposite side of the lever from the top jaws, the upward thrust generated counteracts some of the jaw force loss. Thus, the counterbalanced lever design has substantially more gripping force at high rpm than that of a non-counterbalanced style, according to Hardinge.

The major advantage of the Sure-Grip power chuck is the configuration of the drawtube that actuates the chuck. Since Hardinge machines all have collet spindles that do not require a collet chuck or adapter, it is a simple matter to remove the collet and quickly mount the three-jaw power chuck when needed. The chuck’s drawtube threads directly into the machine’s drawbar, just as a collet would. This change-over can be accomplished in ten minutes or less. The Sure-Grip power chuck is also available for non-Hardinge lathes that do not have collet style spindles.

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